Microbes are diverse and active in the "not-so-dead" zone of Lake Erie
Ann Arbor, MI — Perhaps the name is just for effect, but the purported "dead zone" in the central basin of Lake Erie should more appropriately be termed the "too alive" zone.
Over the past six years researchers have been working to develop a better understanding of the low oxygen region that forms every July through September in the bottom waters of the central basin of Lake Erie. As a start to understanding this process, researchers at the University of Tennessee, Bowling Green State University (Ohio) and Environment Canada have characterizing the organisms that consume most of the oxygen. Although small in size, highly abundant bacteria in the bottom waters of the lake grow at such a rate that they consume the majority of the oxygen in the system during late summer, making life difficult for fish and other organisms.
This decrease in oxygen is important not only from a fisheries viewpoint, but also for a better understanding of lake function as a whole. During conditions of plentiful oxygen, bacteria consume and break down decaying plant and animal material using aerobic (oxygen-dependent) pathways. However, when oxygen concentrations drop to low levels, anaerobic (a term meaning "without air") pathways take over and break down decaying material differently. An important fact in understanding how these processes are intertwined is that some of the nastiest compounds humans have produced (such as PCBs and PAHs) require both pathways in order to be degraded. As such, the perceived seasonal Lake Erie cycle of aerobic - anaerobic - aerobic pathways may help the microbes clean up contaminants in the Lake.
During their study of microbial diversity, the researchers were surprised to find a population of small photosynthetic microorganisms (cyanobacteria known as Synechococcus) deep in the water column. Upon closer examination, it appears these organisms are highly abundant and happily growing, producing an excess of more than 18,000 tonnes of oxygen per day during observations in this study. As such, it now appears that the anaerobic - aerobic - anaerobic cycle may not occur seasonally, but daily, providing more opportunity for bioremediation of synthetic contaminants.
Original Publication Information
Results of this study "Seasonal Hypoxia and the Genetic Diversity of Prokaryote Populations in the Central Basin Hypolimnion of Lake Erie: Evidence for Abundant Cyanobacteria and Photosynthesis," are reported by Steven W. Wilhelm, George S. Bullerjahn, Melanie L. Eldridge, Johanna M. Rinta-Kanto, Leo Poorvin and Richard A. Bourbonniere in the latest issue (Volume 32, No. 4, pp. 657-671) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2006.
Contacts
For more information about the study, contact Steven Wilhelm, Department of Microbiology, The University of Tennessee, Knoxville, TN 37996; wilhelm@utk.edu; (865) 974-0665.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.